Researchers Show How Easy a New Stuxnet-Like Attack Can Be

One of the great residual concerns about the Stuxnet computer worm that attacked the Iranian nuclear program has been that study of its methods would lead to other attacks like it.

Those fears were theoretical for a while. If you could attack the industrial computers controlling nuclear centrifuges and make them explode, as happened in the case of Stuxnet, you could, in theory, use the same approach to attack industrial computers controlling critical infrastructure in the U.S. The only thing needed is knowledge about vulnerabilities lurking in those systems.

The bad news is that, as of yesterday, those vulnerabilities are no longer a theory. The good news is that the good guys found them first.

Yesterday, researchers for a volunteer program called Project Basecamp have discovered three vulnerabilities inside a common model of industrial computer known as a programmable logic controller (PLC). These PLCs basically sit between a regular computer running Windows and a big piece of industrial equipment — say, a pump or a generator or a nuclear centrifuge.

PLCs are part of a larger set of industrial computers known as Supervisory Control And Data Acquisition (SCADA) systems. Security research into SCADA systems has increased dramatically since the revelation of the Stuxnet worm in 2010.

The work was done by researchers at Digital Bond, a security research firm specializing in work on SCADA systems. What they built was a software module called “modiconstux,” which carries out a Stuxnet-like attack on a PLC device called a Modicon Quantum, made by Schneider Electric.

Borrowing techniques learned from the Stuxnet worm, modiconstux does two things: It downloads the current set of instructions the PLC is using — a set of programming commands known as “ladder logic” — giving the attacker the ability to understand what the PLC is doing day in and day out. This is key: If you’re going to hijack a PLC to make the machine it’s controlling explode, you have to first understand the process you’re going to sabotage.

The second thing that modiconstux does is upload new ladder logic. The classic example I think of in explaining this comes from the first public demonstrations of Stuxnet carried out by researchers at Symantec. In that case, a Siemens PLC had been programmed to blow up a balloon by instructing a pump to send a certain amount of air to the balloon and then stop. After being hijacked by Stuxnet, the logic was changed in such a way that the pump didn’t stop, and the balloon popped. Not very menacing, but if you use your imagination, you can see that popping balloon as a metaphor for a lot of very dangerous outcomes.

What’s even scarier than the outcome is the fact that the exploit works without any actual computer hacking having to take place beforehand. Dale Peterson, Digital Bond’s CEO, said the attack works because the PLC is insecure in the first place. There isn’t so much as a password required to download the existing ladder logic, nor to upload the altered ladder logic. And if that PLC is connected to the Internet in any way, it is wide open to attack.

The team also released two other vulnerabilities. One tells the same Scheider Electric PLC to stop, essentially freezing it in place until it can be reset. The third is a vulnerability for a type of PLC device made by General Electric.

The vulnerabilities have been released to the wider world through Metasploit, an open source vulnerability monitoring service that’s owned by Rapid7, a Cambridge, Mass-based company that specializes in helping companies stay ahead of new computer security vulnerabilities. Metasploit subscribers can download the exploit code and test it on their own systems, and demonstrate simulated attacks that in all likelihood will scare the heck out of their bosses.

It should also scare the heck out of legislators and policymakers who have talked incessantly about the need to prepare for a “cyberattack.” Chances are, the next time there’s a serious conflict, attacks carried out by way of a computer will be used to sabotage infrastructure, sow confusion, interfere with logistics and so on. Stuxnet proved what could be done, and what to that point had generally been considered only a theory.

Created by parties unknown — though the smart money says it was Israel, with some help from the U.S. — the Stuxnet worm burrowed its way into PLCs at an Iranian nuclear installation, made the centrifuges spin too fast, and caused some of them to explode. The Iranian nuclear enrichment program was thought to be set back by anywhere from one to two years.

Since then, researchers have been on the lookout for the next Stuxnet, assuming that a second worm would be easier to construct. They’ve also been studying the inherent weaknesses in SCADA systems like PLCs. What they’re finding should give us all pause.

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